[PATCH v2 08/22] iommufd: Abstract iopt_pin_pages and iopt_unpin_pages helpers

[Tian, Kevin]

> From: Nicolin Chen <nicolinc at nvidia.com>
> Sent: Wednesday, May 7, 2025 3:37 PM
> 
> On Wed, May 07, 2025 at 07:22:24AM +0000, Tian, Kevin wrote:
> > > > any reason why this cannot be done by the core? all types of vcmd
> > > > queues need to pin the guest buffer pages, no matter the IOMMU
> > > > accesses GPA or HPA.
> 
> > > But I am doing in the core. I have iopt_pin_pages() called in the
> > > core ioctl handler iommufd_vqueue_alloc_ioctl():
> 
> > IMHO we just want to keep the pin logic in the core while leaving
> > the check of PFN continuity to the driver (or have a way for the
> > driver to communicate such need to the core).
> >
> > It's possible for have an implementation with IOMMU accessing
> > GPA of the queue which further goes through the stage-2
> > translation. In such case it's fine to have disjointed PFNs.
> 
> That makes sense. In the iommufd_viommu_ops structure, we can add
> "u32 flag" where driver can define IOMMUFD_VQUEUE_CONTIGUOUS_PFNS?
> 

that works.